Best?

The network relies on up's, and you have to have a good connection to be one.

If you want to leech, don't be an UP, because UP's donate bandwidth for everyone else's searches.

It's best for the network to be an ultrapeer. Without enough Ultrapeers, new users or users with slow or badly configured connections can't get connected or get decent results.

check out http://www.limewire.com/english/content/netsize.shtml

the red line shows the UP's; the green shows all the others.